The present invention relates to a rodder for cleaning an air port in the wall of a recovery boiler. More particularly, the present invention is an alignment and safety system which allows for the adjustment of the rodder tip or cutter relative to the air port and prevents accidental drifting of the cutter into the air port upon a loss of power to the extension/retraction actuator of the rodder.
Port rodders are provided on recovery boilers to clean the primary air ports or openings, keeping them free from combustion by-products and other deposits commonly referred to as char. By frequently cleaning the port openings, air flow is uniform from all ports into the boiler thus facilitating a high rate of heat transfer and optimum operation.
A rodder generally consists of a tip or cutter mounted on the end of a ram which is in turn connected to an actuator which causes the ram to be extended or retracted. One such actuator would be a pneumatic cylinder. Extension and retraction of the cylinder causes the cutter to move in and out of the port. When extended into the port, the cutter contacts and dislodges the char by cutting and/or pushing it through the port and into the boiler.
Typically, a windbox is mounted on the exterior of the boiler so as to enclose at least one port. Air is supplied to the windbox and will pass through the enclosed port into the interior of the boiler. As the uniformity of the air flow is increased, so is the thermal and chemical reduction efficiency of the boiler. Unfortunately char tends to deposit on the interior surfaces of the boiler and build-up around the air ports. If left unchecked, the char will restrict the opening of the port and thereby inhibit uniform air flow.
Since a windbox is typically used to provide air to the boiler, rodders are mounted so as to extend through the windbox and into the port opening. The actuator, itself is generally mounted exteriorly of the windbox.
One problem encountered when using a port rodder is ensuring proper alignment between the cutter and the port opening. The problem exists because of broad tolerances between the air port castings and the mounting location of the rodder. Additionally, the cutter may extend over four feet from the exteriormost wall of the windbox with the actuator being positioned a distance therebeyond. If severely misaligned, it is possible that the cutter will bind within the air port.
Adjustments to the alignment of the port rodder have generally been limited to moving the cutter's position in a generally x-y plane relative to the port opening. Rotational alignment of the cutter (about its insertion axis) was limited to the play and sloppiness exhibited in the fit where the ram entered the windbox.
Additionally, port rodders which are mounted in an inclined position are capable of accidentally drifting into the port. When the rodder is mounted at an angle relative to the boiler, a loss of actuator power might enable the ram and cutter to be gravitationally extended into the port resulting in damage to the cutter. When extended as described above, long periods of exposure to the internal temperatures of the boiler result in the cutter edges becoming burned and distorted, thereby making the cutter inoperative or, at a minimum, less efficient. Once damaged, the cutter must be replaced resulting in increased operating expenses.
Since the rodder may be mounted with a downward inclination, it is an object of this invention to provide a means for preventing damage to the cutter because of the cutter drifting into the port opening upon a loss of power to the actuator.
It is also an object of the present invention to provide a port rodder with an anti-drifting mechanism while maintaining a highly adjustable alignment mechanism, one which readily enables vertical, horizontal and rotational adjustment of the cutter relative to the port opening.
An additional object of the present invention is to provide an anti-drifting rodder where significant misalignment between the actuator and ram will not cause excessive binding, stress or fatigue in either part.
In achieving the above mentioned objects, the rodder of the present invention is mounted to a wallbox that is attached to a windbox covering port at least one opening of a recovery boiler. The ram and cutter are positioned inside of the windbox while the actuator and alignment mechanism are positioned outside of the windbox and wallbox. Furthermore, the rodder is mounted with a downward inclination such that the cutter is positioned below the actuator.
The rodder is attached to the alignment mechanism, which is in turn secured to a mounting plate assembly of the wallbox. The alignment mechanism is provided with two plates. The first or exterior plate secures the actuator and is mounted to studs or posts extending from the wallbox mounting plate assembly. The first plate is attached to the studs in a manner which will permit the cutter position to be adjusted in a generally horizontal and vertical fashion relative to the port. The distance which the studs extend from the wallbox mounting plate assembly permits the first plate to be moved toward or away from the mounting plate assembly. This movement adjusts the axial distance that the cutter can be inserted into the port. The horizontal and vertical adjustments are made by shifting or tilting the first plate on the studs. To achieve this, the first plate is provided with clearance holes or bores and spherical washers. Through the incorporation of the spherical washers, the first plate, and the rodder, can be positioned at an angle relative to the wallbox mounting plate assembly without imparting bending loads on the studs.
A second or interior plate is positioned adjacent to the first plate. The second plate is releasably secured to the first plate so as to permit rotational movement about the insertion axis. To actually rotate the cutter, the second plate is fixably secured to a support housing in which the ram is disposed. When the second plate is rotated, the support tube causes the ram, and subsequently the cutter, to also rotate. Thus, the ram is disposed in the support housing in a way which will prevent relative rotation therebetween.
A coupler is provided to connect the actuator to the ram. The coupler allows for substantial misalignment between the extending portion of the actuator and the ram without affecting the overall operation of the rodder. The coupler is positioned between the ram and the extension rod of the actuator, respectively on the ends thereof.
The rodder is further provided with the anti-drift mechanism. Between cleaning strokes, fluid source pressure is supplied to the actuator to hold the cutter in its retracted position. This is the normal holding condition. A decrease or loss of fluid source pressure during the holding condition can result in gravitationally induced movement of the cutter towards the port. Such movement is now prevented by the incorporation of the anti-drift feature, two embodiments of which are disclosed. In one embodiment, if fluid source pressure is lost or decreases during the holding stage of operation, the back pressure of the fluid on the retraction side of the actuator will cause a check valve positioned in the source line to become engaged. The closing of the check valve thereby traps any remaining fluid on the retraction side of the actuator preventing extension of the cutter toward the air port. Alternatively, a frictional member, having a number of inwardly extending resilient fingers is positioned between the actuator and the first adjustment plate. The fingers are sufficiently stiff to engage the rodder and stop drift, but are resilient enough to allow for the "powered" passage of the rodder and subsequent extension of the cutter.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings.